Blood flow restriction (BFR) training is increasing in popularity in fitness and rehabilitation settings due to growing evidence of its application and its enhanced role in optimising muscle mass and strength, vascular capacity, function, and other benefits.
So, what is blood flow restriction (BFR)? Blood flow restriction training (BFRT) is a method of resistance training that involves the deliberate reduction of blood flow through a limb, typically using a pneumatic tourniquet/cuff system, to bring about short periods of ischemia during which low-intensity resistance training is undertaken.[1]
Initially, BFR training was developed in Japan in the 1960s. It went by the name of ‘KAATSU’ training and was developed by Dr. Yoshiaki Sato. ‘KAATSU’ means ‘training with added pressure’ and involves the application of a pneumatic cuff nearest to the muscle that is being trained. This cuff is applied to either the lower or upper limbs and is then inflated to a specific pressure. The aim is to obtain partial arterial and complete venous occlusion (BFR).[2]
Once this is done, the patient is asked to perform several resistance exercises at a low intensity of 20-30% of 1 repetition max (1RM) and a predetermined number of sets and repetitions. However, it’s known to be the most effective when repetitions are higher (15-30) with short rest intervals between sets (30 seconds). Typically the intended repetition scheme for BFR exercise is 30-15-15-15 for a total of 75 repetitions for one BFR exercise.[3]
As far as the evidence suggests, BFR training is the real deal!
How does Blood Flow Restriction (BFR) work?
There are different suggestions to how BFR works; however, the current understanding is that BFR training works through the indirect effect of metabolite accumulation and the hypoxic environment from exercising with the restricted arterial flow.
The subject performs a predetermined number of sets and repetitions of an exercise at a lower intensity with the cuff only being deflated. This cuff is then removed after all sets and repetitions are completed. Research shows that BFRT coupled with a load intensity of 20-50% results in muscle mass/muscle strength increase to a degree similar to higher intensity, heavy load training.[4]
Another study demonstrated that resistance training intensities as low as 20% 1RM coupled with BFRT resulted in muscular hypertrophy. [5]
BFRT leads to:
- Fatigue
- Muscle activation
- Anabolic signalling pathways that lead to muscular adaptations
Enhancing the sports performance of experienced and trained athletes is a permanent challenge for sports professionals, with coaches always aiming to find a method to create a greater physiological adaptation.
It’s no secret that gaining muscle size and strength requires a combination of load and volume but what is one to do when a person can’t tolerate heavy loads, i.e., in injury cases?
Simple: BFR training! BFR training can be beneficial in such a case as the same muscle-building ingredients are released through BFR and low-load training.
Through this process, multiple pathways are activated that increase muscle protein synthesis, and a snowball effect occurs. Limited oxygen in the region accelerates fatigue and the recruitment of higher threshold motor units. [6]
Furthermore, there’s another benefit in the shape of a ‘muscle pump’ from the cellular swelling. When the cuff compression is relieved, the blood flow resumes and brings about the physiological processes involved in protein synthesis and muscle building.[7] [8]In traditional resistance exercise, loading the muscle stretches the sarcomeres leading to cytoskeletal matrix damage. An inflammatory cascade follows to build muscle. During BFR, measures of muscle damage such as creatine kinase, lipid peroxides, torque output of muscles, and delayed onset muscle soreness (DOMS) are minimally elevated. Meaning in our muscle growth formula, we don’t have muscle protein breakdown and therefore greater net gains![9] [10]
Physiological adaptations to Blood flow restriction trainingPractical application of Blood Flow Restriction Training
Now that we know how BFR training works let’s talk about its benefits in sports performance. Three areas have benefited from BFR training as it applies to sports performance and rehabilitation. We will discuss each of them.
1. Sports Performance – muscle hypertrophy and managing training load
2. Injured Athletes and post-operative patients
3. Older deconditioned people
- Professional athletes and S&C coaches may find that managing the training load has become more straightforward and more practical with BFR training. Improving strength and muscle mass with minimal mechanical stress with BFR implementation is possible. BFR can help counter the potential adverse effects of high overall training loads that may be typically brought about by increased gym work, extensive travel, and multiple fixtures in a condensed season. A study in Denmark by Aagaard et al. (2020) showed how alternating periods of BFR training with heavy load training led to similar improvements in strength and did not compromise type II myofiber size in trained athletes.[11]
- The injured athletes want to make sure their time out of the sport is minimised, and BFR training is excellent for this. Athletes that are injured can’t put a heavy load on the injured area. This becomes an issue with someone who wants to recover and gain strength simultaneously. Athletes and patients can use BFR training to get a high training effect at a low load, and the injured area will remain protected and stay strong.
The challenge faced by Therapists in Rehabilitation Settings
In patients suffering from patellofemoral knee pain, patients who performed low load BFR exercises showed similar improvements in strength and hypertrophy, with no significant difference in pain measures when compared with standard quadriceps strengthening performed with higher loads. BFR has shown may be a useful alternative for people with PFP who are not tolerating a load of standardised quadriceps strengthening programmes due to pain.[12]
Furthermore, it has been documented that BFR can have an analgesic effect and reduce pain sensitivity remotely and locally for up to 24 hours after application, which is beneficial in the injury rehabilitative process to increase patients’ tolerance to load [13]
Post-operative patients are the ones that have come to the clinic following an ACL reconstruction, Achilles repairs, knee replacements, etc. Theoretically, the application of BFR pre-surgery would benefit patients following orthopaedic surgeries such as anterior cruciate ligament (ACL) reconstruction, as less muscle mass and strength need to be regained in the rehabilitation phase.[14]
Obta et al (2005)
Older deconditioned people can utilise BFR training to strengthen the muscles around the arthritic hips or knees without causing joint pain. It’s also ideal for patients who don’t have strength in their legs. [15] [16]
Some practical applications of BFR training are:
- BFR-RE (resistance training) – micro-dosing
- BFR-AE (aerobic training)
- P-BFR (passively without exercise)
BFR-RE (resistance training) has been shown in a series of studies to effectively be used at an increased frequency to induce adaptations in strength and muscle mass. From an athletic perspective, we could consider parts of the season where we could use periods of micro-dosing BFR to allow the athlete to get the adaptations desired.
For optimal results in BFR-RE (resistance training), it should be done ideally 2-4 times every week. Training 1-2 times per day should only be done for short periods of 1-3 weeks to avoid heavy training loads. This training frequency stimulates muscle hypertrophy without muscle swelling and damage. [17]
BFR – RE can either be completed with compound movements e.g. squats, or single-joint exercises, e.g. knee extensions. A load of 20-40% 1RM has been reported to produce consistent muscle adaptations in this scenario. The most used training volume is 75 repetitions across four sets. The rest period is set between 30-60 seconds [18]
For the best results in BFR-AE (aerobic training), BFR training should be utilised when walking or cycling. BFR training has improved V02 max in cyclists following low-intensity cycling and also improved V02 max in trained basketball players following an intervention. [19] [20]
However, most studies that investigated the effects of BFR training on aerobic performance have been on untrained individuals or have shown scarce and controversial results that make it impossible to draw firm conclusions. Coaches, therefore, should understand that it does not always produce similar benefits and adaptations to standard aerobic training.
A recent systematic review on the effects of BFR on aerobic training demonstrated that including BFR in the training sessions produces significant improvements from baseline measures in aerobic capacity in trained individuals; however, these results are not better than those observed after the same training sessions without BFR.[21]
P-BFR (passively without exercise) research has shown positive results in ischemic preconditioning before exercise performance in endurance and aerobic activities, and also the potential positive effects in improving recovery. [22] [23] [24] Ischemic preconditioning (IPC) is a term used to describe the exposure to brief periods of circulatory occlusion and reperfusion to protect local or systemic organs against subsequent bouts of ischemia
Further research is needed to standardise cuff pressures prescribed for athletes due to the size and variation in muscle mass among different athletic populations.This highlights that better knowledge of the mechanism suggested by the IPC intervention would make it possible to optimise the protocols. [25]
The work by Patterson et al. (2019) brought together much of the current research on BFR training. In addition, the author’s research guidelines for BFR are well documented, focusing on the methodology, application, and safety of this mode of training which is well supported within the literature.[26]
Included with this study are guidelines for BFR-RE and BFR with aerobic exercise and passive BFR while providing clear guidance for the pressures, sets, reps, etc., that should be used when employing the BFRT technique.
Conclusion
BFR training is an emerging safe and effective clinical modality that can obtain physiological adaptations for people who have trouble safely tolerating high-load exercise and stress during congested fixtures.
It can effectively be micro-dosed in training plans to induce muscle hypertrophy and strength, in addition to helping with the management of pain and injuries. There is also growing evidence that BFR can cause acute performance enhancement and promote recovery from training.
(BFR) is known to induce significant gains in muscle strength and size, and be effective in improving endurance qualities in trained and untrained athletes. This mode of training is increasingly used in both healthy and clinical populations, as documented in the recent review by Patterson et al. (2021).[27] While the results of BFR training are positive, continued research is required in BFR training to ensure safety and standardised applications among different athletic populations.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5609669/
[2] https://doi.org/10.3806/ijktr.1.19
[3] https://doi.org/10.3389/fphys.2019.00533
[4] https://pubmed.ncbi.nlm.nih.gov/28500081/
[5] https://pubmed.ncbi.nlm.nih.gov/10846023/
[6] https://pubmed.ncbi.nlm.nih.gov/32324471/
[7] https://pubmed.ncbi.nlm.nih.gov/22802591/
[8] https://pubmed.ncbi.nlm.nih.gov/16339340/
[9] https://pubmed.ncbi.nlm.nih.gov/20150565/
[10] https://www.frontiersin.org/articles/10.3389/fphys.2012.00392/full
[11] https://doi.org/10.1111/sms.13632
[12] https://pubmed.ncbi.nlm.nih.gov/28500081/
[13] https://pubmed.ncbi.nlm.nih.gov/32105522/
[14] https://pubmed.ncbi.nlm.nih.gov/12635796/
[15] https://pubmed.ncbi.nlm.nih.gov/21727301/
[16] https://pubmed.ncbi.nlm.nih.gov/20682613/
[17] https://doi.org/10.3389/fphys.2018.01448
[18] https://pubmed.ncbi.nlm.nih.gov/23446173/
[19] https://doi.org/10.1007/s00421-010-1377-y
[20] https://pubmed.ncbi.nlm.nih.gov/24149640/
[21] https://doi.org/10.1016/j.jesf.2022.03.004
[22] https://doi.org/10.1007/s40279-015-0433-5
[23] https://pubmed.ncbi.nlm.nih.gov/11128848/
[24] https://pubmed.ncbi.nlm.nih.gov/29867526/
[25] https://doi.org/10.1016/j.jshs.2019.01.008
[26] https://doi.org/10.3389/fphys.2021.566421
[27] https://doi.org/10.3389/fphys.2019.00533
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